Problemy z Przepełnieniem stosu w NET9.0

public static string PodpiszXmlKSeF(string xmlTresc)
{
    X509Certificate2 cert = WybierzCertyfikat();
    if (cert == null) return null;

    XadesService xadesService = new XadesService();
    SignatureParameters parameters = new SignatureParameters
    {
        SignaturePackaging = SignaturePackaging.ENVELOPED,
        SignatureMethod = SignatureMethod.RSAwithSHA256,
        DigestMethod = DigestMethod.SHA256,
        Signer = new FirmaXadesNetCore.Crypto.Signer(cert)
    };

    byte[] xmlBytes = Encoding.UTF8.GetBytes(xmlTresc);

    using (MemoryStream msIn = new MemoryStream(xmlBytes))
    using (MemoryStream msOut = new MemoryStream())
    {
        // 1. Podpisujemy strumień wejściowy
        var signatureDocument = xadesService.Sign(msIn, parameters);

        // 2. Zapisujemy wynikowy SignatureDocument do strumienia wyjściowego
        signatureDocument.Save(msOut);

        // 3. Konwertujemy bajty ze strumienia na string UTF-8
        return Encoding.UTF8.GetString(msOut.ToArray());
    }
}

[UnmanagedCallersOnly(EntryPoint = "AuthorizeToken",
        CallConvs = new[] { typeof(CallConvCdecl) })]

    public static int AuthorizeToken(IntPtr url_IP,IntPtr nip_IP, IntPtr token_IP, IntPtr buffer, int bufferSize)
    {
        string url = Marshal.PtrToStringUni(url_IP);
        string nip = Marshal.PtrToStringUni(nip_IP);
        string token = Marshal.PtrToStringUni(token_IP);
...

        response = client.Execute(request);

        string text = response.Content ?? "";
        byte[] data = System.Text.Encoding.Unicode.GetBytes(text + "\0");
        int bytesToCopy = Math.Min(data.Length, bufferSize); 
        Marshal.Copy(data, 0, buffer, bytesToCopy);
        return text.Length; // długość znaków
}

...
function AuthorizeToken(url: PWideChar; nip: PWideChar; token: PWideChar; Buffer: PWideChar; BufferSize: Integer): Integer; cdecl; external 'NKsef9.0.dll';
...


procedure TForm4.Button2Click(Sender: TObject);
var
  buf: array [0 .. 200000] of WideChar;
  len: Integer;
...

begin
  len := AuthorizeToken(PWideChar(url), PWideChar(Edit5.Text), PWideChar(Edit6.Text), buf, SizeOf(buf));
  Memo1.Text := buf;

end;